Inheritance: extends DatastoreClientStub
 public function testLookup()
 {
     $ds = new DatastoreClientStubNoService();
     $key = $ds->key('Kind', 'Value');
     $res = $ds->lookup($key);
     $this->assertInstanceOf(Entity::class, $res);
     $this->assertTrue($ds->didCallLookupBatch);
     $this->assertEquals($key, $ds->keys[0]);
 }